The present invention broadly relates to a headbox for a papermaking machine and, more specifically pertains to a new and improved apparatus for adjusting a diaphragm blade or the like at an outlet gap or slice or slice opening of a headbox.
Generally speaking, the apparatus of the present invention is of the type comprising driveable adjusting elements which are arranged in an appropriate spaced relationship substantially parallel to the diaphragm blade and coupled with the latter in order to apply at connection locations a force upon the diaphragm blade. The adjusting elements are supported at a rigid stationary support or carrier.
As is known to the art, the diaphragm blade or leaf is designed to be displaceable vertically or perpendicular to the paper stock flow in the outlet gap or slice or slice opening of the papermaking machine and serves for the adjustment of the clearance or inner width or height of the outlet gap or slice over the entire width or cross-machine extent thereof. The adjustment of the diaphragm blade from an actual position or location to a reference or set position or location is accomplished, while undergoing elastic deformation of the diaphragm blade in the region of the connecting locations between the adjusting elements and the diaphragm blade, by applying the required force. Such force is applied via the adjusting elements which are moved or displaced in a corresponding direction through a corresponding thrust distance or travel and stopped and arrested after reaching the predetermined end points or terminal locations of the reference position of the diaphragm blade.
According to a prior art adjusting technique or method with the hitherto used apparatus, the adjusting elements are moved either individually or in groups or collectively during a collective simultaneous movement of several adjusting elements, all such adjusting elements having approximately the same thrust speed, with the exception of possible acceleration or deceleration operations. Since the thrust distances to be covered for adjusting a reference position of the diaphragm blade or leaf, particularly according to a curve, are of different lengths, some end points or terminal locations are reached earlier than others at the same thrust speed for all involved adjusting elements. In the region of each end point or terminal location already reached, undesired bending stress can occur in the diaphragm blade. Such bending stress can possibly lead to a permanent plastic deformation of the diaphragm blade or leaf, although the diaphragm blade adjustment to be performed from the actual position or location to the reference position or location thereof would lie in any event in the range of the elastic deformability of the diaphragm blade.